RAYNHAM — The charred sites began appearing across Southeastern Massachusetts in late September, a growing cluster of at least 16 suspicious fires from Quincy to Sandwich that is feared to be the destructive work of a serial arsonist.

The latest fire, ruled an ­arson, happened late Monday night in a vacant outbuilding at the old Raynham dog track, ­only one day after another unexplained fire erupted at a building in Weymouth.

State and local fire officials are intensifying their investigation, hoping to put a quick end to the random torching of ­vacant buildings, homes, and sheds for what might be the simple thrill of momentary excite­ment.

“We ask the public to be vigilant,” State Fire Marshal ­Stephen Coan said Tuesday ­after the Raynham blaze had been extinguished. “Investigators believe this fire may be connected to the series of fires.”

Many of the fires have ­occurred at night, in secluded areas, and in unoccupied buildings, apparently set for excitement rather than revenge, profit, or to injure. An arsonist with such motivations, federal studies show, is typically a single white male with a criminal ­record and limited education.

So far, no one has been ­injured. But the worry caused by the fires has spread through many of the small, semirural communities that stretch south of Boston toward Cape Cod.

“It’s a cause of anxiety for the public, and the best thing we can do to relieve that anxiety is to catch whoever is setting these fires,” said Jennifer Mieth,
spokeswoman for the state fire marshal. “We’re relying heavily on the public to be our eyes and ears.”

Mieth said fire officials have received many leads, but she would not discuss why they ­believe the fires are linked.

“These are the kinds of things that the investigators want to keep close to the vest,” Mieth said. “Whenever we’re interviewing anyone, we don’t want them to have this information, so we’ll know whether they’re telling us the truth.”

In Raynham, the fire was set in a one-story storage building that once had been used to shelter dogs and their owners ­between races, said Fire Chief James T. Januse. The former track is now used for simulcasts, following voters’ decision in a 2008 state referendum to ban greyhound racing.

The blaze began shortly ­before 10 p.m. Monday and was extinguished in about 40 minutes, fire officials said.

James Alan Fox, a Northeastern University professor of criminology, said ]thrill-seeking arson often involves more than one person, a team that derives pleasure from the bonding ­aspect of setting the fire. “The fires tend to be secondary to the sense of their relationship, a ­secret activity that binds them together,” Fox said. “There’s this camaraderie that they get out of doing this.”

The serial arsonist motivated by the thrill of the fire often finds fuel in available materials — wood, paper, leaves — and sets the blaze with matches or other simple devices, said a 1990s study by academics and federal agencies.

The arsonist does not take souvenirs and often travels to another location to watch firefighters battle the blaze, according to the study, conducted for the National Center for the Analysis of Violent Crime.

“Once he has viewed the damage, he loses all interest in the fire and returns to his usual lifestyle and behavioral patterns,” the study said.

The arsonist in this case, or the team, is “betting on the idea they won’t get caught,” Fox said. “They can well justify it to themselves that no one’s getting hurt, it’s only property, and the insurance companies will pay for it anyway.”

Along with the excitement, he said, the arsonist’s motivation includes “getting a sense of power out of destroying property and outsmarting the police. Part of the thrill that one may get is the sense of importance and superiority.”

Some arsonists return to the scene, after firefighters have ­arrived, to revel in the excitement. In doing so, however, they might provide clues that lead to their arrest.

Firefighters and security workers have also been counted among the ranks of thrill-seeking arsonists, driven sometimes by boredom or by a longing for recognition in responding to a blaze, the federal study said.

Southbridge Fire Chief Mark DiFronzo said taking photographs of the crowds at fires can be helpful. If a string of ­arsons has happened, he said, a person’s presence at each blaze would be suspicious.

DiFronzo, whose department is in Central Massachusetts, said that finding the arson­ist responsible for the ­recent fires could be difficult because they have occurred over a fairly wide area.

“It can be frustrating,” ­DiFronzo said. “You’re hoping the person makes a mistake, and you’re hoping the mistake doesn’t cost someone his life.’’

Anyone with information on the fires is asked to call the ­Arson Hotline at 800-682-9229. Rewards of up to $5,000 may be available.

Globe correspondent George Rizer and John R. Ellement of the Globe staff contributed to this report. Brian MacQuarrie can be reached at macquarrie@globe.com.